Although Attorney General Jeff Sessions asserted that a change in federal policy that could lead to more marijuana prosecutions in states that have legalized the drug merely restored the rule of law, Republicans in those states could end up paying a high political price in November’s midterm elections for the Trump Justice Department’s stance on the issue.

In a memo released Thursday, Sessions advised federal prosecutors to decide for themselves how aggressively to enforce federal marijuana laws, which conflict with state laws in more than half of the country. Most states allow legal use of the drug in some form, but federal law still classifies it as a controlled substance on par with heroin.

“Today's memo on federal marijuana enforcement simply directs all U.S. Attorneys to use previously established prosecutorial principles that provide them all the necessary tools to disrupt criminal organizations, tackle the growing drug crisis, and thwart violent crime across our country,” Sessions said in a statement.

The memo reversed an Obama-era policy that directed federal prosecutors to deprioritize marijuana cases so their strained resources could be applied to cartels and traffickers. The Justice Department issued that guidance in 2013 after states began decriminalizing recreational marijuana.

Thursday’s DOJ announcement came just four days after California became the sixth state to allow the legal recreational sale of marijuana, joining Alaska, Colorado, Nevada, Oregon, and Washington. Voters in Massachusetts and Maine have approved legalization, but sales have not yet begun. The District of Columbia has legalized possession and growth of recreational marijuana, but not the sale of it.

Twenty-nine states have approved the use of medicinal marijuana to some degree, and growers and dispensaries in those jurisdictions have been left with many questions by Sessions’ decision.

States that have legalized marijuana credit the industry with creating jobs, generating tax revenue, and scaling back the black market for the drug. In Oregon alone, Gov. Kate Brown said it has provided 19,000 jobs and $100 million in taxes over the last year and a half.

As of mid-2017, there were there were more full- or part-time workers in the cannabis industry in the U.S. than dental hygienists and bakers, according to Marijuana Business Daily. The trade publication’s research also projects total sales of medical and recreational marijuana to hit $9 billion this year.

Critics point to crimes and accidents caused by people under the influence of marijuana, edibles appealing to children, and concerns about addiction and long-term mental effects of smoking as reasons to reverse the legalization trend.

Though legal experts have said it is unclear whether this change will ultimately result in more prosecutions or targeting of legitimate marijuana businesses—several U.S. attorneys have already said they do not intend to alter their approach to marijuana violations—the announcement promptly tanked cannabis stocks Thursday.

A bipartisan mix of members of Congress and officials from states that have legalized marijuana swung back hard at Sessions on Thursday.

“This is outrageous,” said Rep. Earl Blumenauer, D-Ore. “Going against the majority of Americans—including a majority of Republican voters—who want the federal government to stay out of the way is perhaps one of the stupidest decisions the Attorney General has made.”

Sen. Cory Booker, D-N.J., who has proposed a bill to legalize marijuana on the federal level, said the Trump administration is on the wrong side of history.

“Jeff Sessions’ determination to revive the failed War on Drugs knows no bounds,” he said. “History has shown that our deeply broken drug laws disproportionately harm low-income communities and communities of color and cost us billions annually in enforcement, incarceration, and wasted human potential, without making us any safer.”

Sen. Cory Gardner, R-Co., called the policy change “extremely alarming” and claimed Sessions had personally assured him marijuana would not be a DOJ priority.

“Today’s action directly contradicts what I was told, and I am prepared to take all steps necessary, including holding DOJ nominees, until the Attorney General lives up to the commitment he made to me prior to his confirmation,” he said in a statement.

Sessions’ move is not without its supporters, though. Some law enforcement officials in counties that have struggled to contain illegal growing and trafficking operations applauded the change.

“This is the kind of leadership that will save lives. For too long law enforcement has been handcuffed by vague and unenforced policy guidance,” Ron Brooks, former head of the National Narcotics Officers Association Coalition, said in a statement.

Advocacy groups that have fought against marijuana legalization welcomed the prospect that the new policy will slow the growth of an industry that they warn could come to rival Big Tobacco in its cultural and political influence.

“This is a good day for public health. The days of safe harbor for multi-million-dollar pot investments are over,” said Kevin A. Sabet, head of Smart Approaches to Marijuana (SAM) and a former Obama drug policy adviser, in a statement. “DOJ’s move will slow down the rise of Big Marijuana and stop the massive infusion of money going to fund pot candies, cookies, ice creams, and other kid-friendly pot edibles. Investor, banker, funder beware.”

Even some conservatives who disagree with Sessions’ stance grudgingly admit he is only trying to enforce existing federal law. If Congress does not like it, they say, Congress can change the law.

“Perhaps Senator Gardner will distinguish himself by taking up the cause rather than demanding that the attorney general do his work for him,” Kevin Williamson wrote in the National Review.

Democrats, for their part, are already eyeing ways to use the expected backlash against the Trump administration for political advantage. Sen. Booker has teamed with MoveOn.org on a petition in support of his Marijuana Justice Act that had nearly 365,000 signatures on Friday afternoon.

Michael Cohen, director of the political management program at the George Washington University Graduate School of Political Management, doubts marijuana has potency as a national issue, but it will influence some votes in specific races. With majorities in the House and Senate on the line in November, every one of those votes counts.

“Every issue has a constituency and there is a group of people for whom this is a top issue,” he said. “They’ll be more likely to research the candidate’s stances on the issue and vote accordingly.”

Certain demographics are more apt to mobilize over pot than others, and there are tight matchups where that enthusiasm will matter.

“In very blue California, it might drive up younger turnout in Republican Rep. Darrell Issa’s race, which is a toss-up,” Cohen said.

According to Democratic strategist Matt McDermott, the Trump administration is out of sync with the American people on this issue, and it may drag some vulnerable western Republicans down with it.

“Republicans are facing a wave election this November,” he said. “In particular, they're facing potential massive loses in places like California and Colorado, both states where voters have decided to legalize marijuana.”

“Marijuana legalization is far more popular than Sessions or Trump; it will survive them both,” Jag Davies, director of communications strategy for the Drug Policy Alliance, predicted in a New York Daily News op-ed.

“This move by the attorney general will prove not just to be a disaster from a policy perspective, but from a political one…. Ending our disgraceful war on marijuana is the will of the people and the Trump administration can expect severe backlash for opposing it,” Erik Altieri, executive director of NORML said in a statement.

Rep. Dana Rohrabacher, R-Calif., does not disagree.

“By taking this benighted minority position, he actually places Republicans’ electoral fortunes in jeopardy,” he said of Sessions in a statement.

A Pew Research Center survey conducted in October found 61 percent of Americans support legalizing the use of marijuana, up only slightly from last year but nearly double the 31 percent that backed it in 2000. Support is much higher among younger generations and Democrats, but a majority of Republicans and Republican-leaning independents under 40 also favored legalization.

A Gallup poll conducted around the same time saw similar results, with 64 percent saying use of marijuana should be legal, including 51 percent of Republicans. Only 12 percent of respondents supported it in 1969 when the question was first asked.

However, an Emerson College survey conducted at the end of November for SAM got different responses by asking a more nuanced question. They asked 600 New York voters if they supported the state’s current policy of legal medical marijuana and decriminalization of possession of small amounts of recreational marijuana or want it changed. Forty percent still backed full legalization, but 26 percent wanted to keep it as it was and 22 percent only wanted to allow medical marijuana use.

The fact that many Republicans have also staked out opposition to Sessions on the issue could complicate the political calculation for Democrats, but McDermott believes it will not blunt their advantage.

“That Republicans from affected states are speaking up is frankly too little too late, and confirms the very foundation of Democrats' message heading into November,” he said. “As long as Republicans control Congress, Donald Trump gets to do whatever reckless thing he wants to do, unfettered.”

Cohen noted that supporting legalization on libertarian grounds has benefited Sen. Rand Paul, R-Ky., for years, particularly among young voters, and Sen. Gardner has framed it as a state’s rights issue, which may appeal to conservatives. However, McDermott suggested Democrats may succeed by emphasizing that the party in power makes policy and the Trump administration tends to get what it wants from a Republican Congress.

“Democrats have one clear message: if you want accountability, if you want a check and balance on the decisions being made by the Trump administration, Democrats must regain control of Congress,” he said.

Even if Democratic politicians remain hesitant to openly embrace legalizing a drug, Arnie Arnesen, a liberal radio host based in New Hampshire, said activists and voters will gladly take up the cause.

“There wasn’t one political figure that supported decriminalization in Massachusetts” when the issue first came up for a vote in 2008, she said, but some state lawmakers were willing to take a stand when a ballot measure passed there in 2016. “That’s liberal left Massachusetts. What does that tell you? The people get it.”

Arnesen predicted the public response may dwarf some of the other issues that sent the anti-Trump resistance marching through the streets last year.

Given the strength of public opinion and his own past statements on the issue, President Trump himself remains something of a wildcard in the debate. NBC News reported the memo and policy change came entirely from within the Justice Department without input from the White House.

On the campaign trail, Trump said the status of marijuana should be decided at the state level. While Sessions’ announcement could directly undermine many state laws, White House Press Secretary Sarah Sanders insisted Thursday that the president’s position has not changed.

“In interviews and in private conversations, Trump has said that he does not want the federal government involved in this issue,” Cohen said. “He might just revert back to this baseline and blame his attorney general, Jeff Sessions, who he has been wanting to get rid of for quite a long time.”